This invention relates to an arrangement of valves for an internal combustion engine and more particularly to an improved arrangement of valves that permits better engine performance while, at the same time, affording a degree of exhaust emission control by simplifying the process of exhaust gas re-circulation (EGR). In addition, the invention provides for a simplification of systems known in the art that provide improved working fluid mixing (fuel+air) and better control of premature ignition through an automatic exhaust gas recycling (EGR) mechanism.
It is well known that a variety of modifications have been incorporated over the years for improving the performance of internal combustion engines and for controlling exhaust gas emissions, and particularly for controlling the emission of hydrocarbons, carbon monoxide and NOx in the exhaust gases. Unfortunately, many of the innovations employed to provide exhaust emission control can deteriorate the fuel economy of an engine while performance enhancement often leads to greater complexity and cost in engine manufacture and maintenance.
One way in which these objectives have been met is through the use of compound induction systems for the engine wherein low and mid-range performance operation is obtained by a single, relatively small intake passage to offer good turbulence in the combustion chamber, while high speed requirements are met by a larger effective passage so as to improve volumetric efficiency in the introduction of working fluid (the combustible gas mixture, fuel/air etc.). Normally this type of compound induction system incorporates at least two intake passages that serve each combustion chamber with a throttle valve arrangement for controlling the flow through one of the intake passages so that it will supply no charge under low and mid-range load conditions. However, the existence of this additional passage and its flow control valve can give rise to pumping losses that deteriorate the fuel economy of the engine when the control valve is closed.
For the control of contaminating gas emissions, in particular NOx compounds that are major smog producing agents, the practice of exhaust gas recycling (EGR) is often incorporated. EGR is found to reduce the combustion temperature of the working fluid in the combustion chamber, thereby reducing the formation of NOx compounds and, at the same time, helping to prevent premature ignition of the combustible mixture which produces the well-known phenomenon knows as engine "knock." Premature ignition is conventionally controlled by adjusting the characteristics of the fuel by the addition of "anti-knock" agents, which are themselves known or suspected environmental contaminants.
It is a principle object of this invention to provide a novel valve arrangement that improves engine performance by reducing the physical limitations placed on conventional valve arrangements in internal combustion engines by what is known in the art as "valve flotation," in which the rate of valve opening and closing is limited by the speed with which the valve actuating mechanisms known in the art can respond physically and thereby complete their intended function.
It is a further principal object of this invention to provide a novel valve arrangement providing for common conduits leading to the combustion chamber of the engine through one or more pre-combustion chambers or plenums in which what may be considered conventional intake and exhaust chambers are openly and directly intercommunicated to form a chamber or chambers that communicate directly with the combustion chamber. Said communication between conventional conduits for induction and exhaust processes for an engine provide improved performance results under all running conditions, while at the same time providing improved exhaust emission control. These goals are achieved while simplifying the mechanical aspects of related current technology.
It is a further object of this invention to provide an improved valve arrangement for induction and exhaust processes for an engine that permits the aforementioned results while, at the same time, eliminating or substantially reducing pumping losses under low and mid-range performance so as to improve fuel economy.
One way in which NOx emissions are controlled is through the use of exhaust gas re-circulation (EGR). Re-circulating exhaust gases into the combustion chamber under at least some running conditions reduces the temperature of combustion and thereby the formation of NOx. However, the use of EGR can give rise to poor running characteristics when large quantities of exhaust gases are re-circulated, especially at high working loads.
It is, therefore, a still further object of this invention to provide an improved system for permitting increased usage of EGR without deteriorating engine performance.
It is a further object of this invention to provide an EGR system for an engine having a compound induction system wherein the EGR is employed to reduce pumping losses as well as controlling the emission of NOx.